On 05.06.24 10:30, ran xiaokai wrote:
On 05.06.24 04:20, ran xiaokai wrote:
On 04.06.24 07:47, xu.xin16@xxxxxxxxxx wrote:
From: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx>
When I did a large folios split test, a WARNING
"[ 5059.122759][ T166] Cannot split file folio to non-0 order"
was triggered. But my test cases are only for anonmous folios.
while mapping_large_folio_support() is only reasonable for page
cache folios.
Agreed.
I wonder if mapping_large_folio_support() should either
a) Complain if used for anon folios, so we can detect the wrong use more
easily. (VM_WARN_ON_ONCE())
b) Return "true" for anonymous mappings, although that's more debatable.
Hi, David,
Thanks for the review.
I think a) is better.
But we have to add a new parameter "folio" to mapping_large_folio_support(), right ?
something like mapping_large_folio_support(struct address_space *mapping, struct folio *folio) ?
But in the __filemap_get_folio() path,
__filemap_get_folio()
no_page:
....
if (!mapping_large_folio_support(mapping))
the folio is not allocated yet, yes ?
Or do you mean there is some other way to do this ?
If we really pass unmodified folio->mapping, you can do what
folio_test_anon() would and make sure PAGE_MAPPING_ANON is not set.
I think I just misunderstood your suggestion.
Likely my use of "folio" was confusing.
How about this ?
static inline bool mapping_large_folio_support(struct address_space *mapping)
{
VM_WARN_ONCE((unsigned long)mapping & PAGE_MAPPING_ANON,
"Anonymous mapping always supports large folio");
return IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
test_bit(AS_LARGE_FOLIO_SUPPORT, &mapping->flags);
}
Yes, and we should likely document that this is not supposed to be used
with mappings from anonymous folios.
--
Cheers,
David / dhildenb
